The invention relates to a bearing and loading arm for drafting units having holding devices for pressure roller twins, which each contain a leaf spring held at the bearing and loading arm by means of a spring retainer which is adjustable in longitudinal direction of the bearing and loading arm, this leaf spring bearing a receiving device for a shaft of the pressure roller twins.
In a known bearing and loading arm of this type described in German utility model (DE-GM) 19 09 951, the holding device has a slider which is used as the spring retainer is held by means of a screw at the bearing and loading arm and can be locked in the respective operative position. The leaf spring is fastened at this slider by means of an additional screw and, at its other end, has the receiving device for the shaft of the pressure roller twin. Between the spring retainer constructed as the slider and the leaf spring, a supporting plate is arranged, which is provided with a slot and can be shifted in longitudinal direction of the leaf spring, and by means of the shifting of which, the effective spring length can be adjusted. The danger exists in this known construction that the shaft of the pressure roller twin is not adjusted in parallel with respect to the pertaining bottom roller. It is possible for the leaf spring to carry out rotations around the screw which holds it at the spring retainer, and it is also possible that the spring retainer itself carries out movements around the screw connecting it with the bearing and loading arm.
An object of the invention is to develop a bearing and loading arm of the initially mentioned type such that the parallelism between the pressure roller twin and the pertaining bottom roller is ensured without any adjusting work.
This object is achieved according to the invention by aligning the leaf spring transversely to the longitudinal direction of the bearing and loading arm on guides.
By means of this construction, it is ensured that the leaf spring itself is aligned with respect to the guides so that adjustments at the spring retainer holding the leaf spring cannot result in a loss of parallelism.
In a further development of preferred embodiments of the invention, it is provided that the leaf spring is fixed in the spring retainer in loading direction and in longitudinal direction of the bearing and loading arm, and that the leaf spring supports itself transversely with respect to the bearing and loading arm directly at this bearing and loading arm. Since an adjustment is required only in longitudinal direction of the bearing and loading arm and possibly may also be required with respect to the loading, these adjustments may be carried out by means of the spring retainer. However, since the leaf spring is guided directly at the bearing and loading arm, these adjustments do not result in a changing of the position of the leaf spring in transverse direction with respect to the bearing and loading arm so that parallelism is maintained with a high degree of certainty without the requirement of having to take special measures for the adjusting of the spring retainer.
In a further development of preferred embodiments of the invention, it is provided that the receiving device for the shaft of the pressure roller twin, after the mounting of the leaf spring, is at least subjected to a finishing. For this purpose, the receiving device is first mounted on the leaf spring, after which the leaf spring with the receiving device is inserted in an arrangement which corresponds to the holding device formed by the spring retainer and the bearing and loading arm and which is aligned precisely with respect to a tool which finishes the receiving device. In this position, the receiving device will then be gripped, held and finished. As a result, it is ensured that the recess of the receiving device, in which the shaft of the pressure roller twin will later be accommodated, is aligned precisely with respect to that area of the leaf spring by means of which it is supported at the spring retainer and later at a bearing and loading arm, without any perceptible occurrence of tolerances which may have been created in the spring as a result of manufacturing. These tolerances are all compensated by the subsequent finishing.
Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of the invention when considered in conjunction with the accompanying drawings.